The robust bistable genetic switch plays a pivotal role in controlling the entry of a cell into alternative developmental states, in the stable maintenance of the chosen state, and in the switching from one stable state to the alternative stable state. This research project expects to establish the important parameters underpinning the operation of the switch, by the comparative analysis of three native genetic switches. These switches control the alternative states of lytic response and lysogeny available to a temperate bacteriophage, a system that is experimentally tractable. In particular, the study aims to establish and comparatively analyze the role of the second repressor, the anti-immune repressor, in the operation of the isolated bistable switch in the context of the genetic network underpinning phage development. Understanding the operation of genetic switches is of fundamental significance to the research programs concerned with the reprogramming of donor cells for cell-based therapy in the "new" medicine and to the development of genetic constructs that will deliver therapeutics to a patient periodically or on queue. Simple genetic switches are already in use in the biotechnology industry for the commercial production of biopharmaceuticals. Finally, a better understanding of the operation of the genetic switch of temperate bacteriophage could be of potential significance in the treatment of bacterial disease, as the pathogenesis of many bacteria is due to the phage that they carry in their genome. Our approach is to make mutations that selectively abolish the activity of the anti-immune repressor in each switch and then to examine the effect of these mutations at three levels: (1) on bacteriophage development, (2) on the behavior of the bistable switch in the absence of other phage genes, and (3) on the autoregulatory gene control circuit that creates the switch. This will provide a coherent picture of how switches are achieved and how they are utilized within genomic networks. [unreadable] [unreadable]